fix: Bug when trying to deserialize a type into itself for Lambda default behavior. We can just return the type itself. Relevant for simple String and InputStream handlers.

Author: phipag

powertools-kafka/src/main/java/software/amazon/lambda/powertools/kafka/serializers/LambdaDefaultDeserializer.java

@@ -28,12 +28,22 @@ public class LambdaDefaultDeserializer implements PowertoolsDeserializer {
     @SuppressWarnings("unchecked")
     @Override
     public <T> T fromJson(InputStream input, Type type) {
-        return JacksonFactory.getInstance().getSerializer((Class<T>) type).fromJson(input);
+        // If the target type does not require conversion, simply return the value itself
+        if (type.equals(InputStream.class)) {
+            return (T) input;
+        }
+
+        return (T) JacksonFactory.getInstance().getSerializer(type).fromJson(input);
     }
 
     @SuppressWarnings("unchecked")
     @Override
     public <T> T fromJson(String input, Type type) {
-        return JacksonFactory.getInstance().getSerializer((Class<T>) type).fromJson(input);
+        // If the target type does not require conversion, simply return the value itself
+        if (type.equals(String.class)) {
+            return (T) input;
+        }
+
+        return (T) JacksonFactory.getInstance().getSerializer(type).fromJson(input);
     }
 }

powertools-kafka/src/test/java/software/amazon/lambda/powertools/kafka/PowertoolsSerializerTest.java

@@ -19,6 +19,7 @@
 import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
+import java.io.InputStream;
 import java.lang.reflect.Type;
 import java.util.Arrays;
 import java.util.Base64;
@@ -108,6 +109,39 @@ void shouldUseLambdaDefaultDeserializer(InputType inputType) throws JsonProcessi
         assertThat(result.getTags()).containsExactly("tag1", "tag2");
     }
 
+    @Test
+    @SetEnvironmentVariable(key = "_HANDLER", value = "software.amazon.lambda.powertools.kafka.testutils.StringHandler::handleRequest")
+    void shouldHandleStringInputType() {
+        // When
+        PowertoolsSerializer serializer = new PowertoolsSerializer();
+
+        // Then
+        String testInput = "This is a test string";
+
+        // This should directly return the input string
+        String result = serializer.fromJson(testInput, String.class);
+
+        assertThat(result).isEqualTo(testInput);
+    }
+
+    @Test
+    @SetEnvironmentVariable(key = "_HANDLER", value = "software.amazon.lambda.powertools.kafka.testutils.InputStreamHandler::handleRequest")
+    void shouldHandleInputStreamType() throws IOException {
+        // When
+        PowertoolsSerializer serializer = new PowertoolsSerializer();
+
+        // Then
+        String testInput = "This is a test string";
+        ByteArrayInputStream inputStream = new ByteArrayInputStream(testInput.getBytes());
+
+        // This should return the input stream directly
+        InputStream result = serializer.fromJson(inputStream, InputStream.class);
+
+        // Read the content to verify it's the same
+        String resultString = new String(result.readAllBytes());
+        assertThat(resultString).isEqualTo(testInput);
+    }
+
     @ParameterizedTest
     @MethodSource("inputTypes")
     @SetEnvironmentVariable(key = "_HANDLER", value = "software.amazon.lambda.powertools.kafka.testutils.JsonHandler::handleRequest")

powertools-kafka/src/test/java/software/amazon/lambda/powertools/kafka/testutils/InputStreamHandler.java

@@ -0,0 +1,30 @@
+/*
+ * Copyright 2023 Amazon.com, Inc. or its affiliates.
+ * Licensed under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package software.amazon.lambda.powertools.kafka.testutils;
+
+import java.io.IOException;
+import java.io.InputStream;
+
+import com.amazonaws.services.lambda.runtime.Context;
+import com.amazonaws.services.lambda.runtime.RequestHandler;
+
+public class InputStreamHandler implements RequestHandler<InputStream, String> {
+    @Override
+    public String handleRequest(InputStream input, Context context) {
+        try {
+            return new String(input.readAllBytes());
+        } catch (IOException e) {
+            throw new RuntimeException("Failed to read input stream", e);
+        }
+    }
+}

powertools-kafka/src/test/java/software/amazon/lambda/powertools/kafka/testutils/StringHandler.java

@@ -0,0 +1,23 @@
+/*
+ * Copyright 2023 Amazon.com, Inc. or its affiliates.
+ * Licensed under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package software.amazon.lambda.powertools.kafka.testutils;
+
+import com.amazonaws.services.lambda.runtime.Context;
+import com.amazonaws.services.lambda.runtime.RequestHandler;
+
+public class StringHandler implements RequestHandler<String, String> {
+    @Override
+    public String handleRequest(String input, Context context) {
+        return input;
+    }
+}